Researchers have noted that active smoke exposure was possibly related to epigenetic mechanism,and may further influence reactive immunotoxicological reaction on human beings. Some studies have been reported that smoking reduction would decrease the prevalence of respiratory symptoms and urinary cotinine level, but the underlying epigenetic mechanism and the functional changes of immunotoxicological system were still unclear. We plan to examine the causal relationship between smoking reduction and alterations in epigenetic signatures/immunotoxicological reactions. Teenager Smoking Reduction Trial (TSRT) will be population-based trial among teenagers. Eligible teenagers will be recruited in Taipei City and urinary cotinine level will be used to monitor the exposure status of active smoking at baseline, 1-month and 3-month of the intervention process. We will assess the potential change in immunotoxicological markers, including Th1/Th2 cytokines and clinical immunological measurements, before and after the intervention program. Furthermore, whole-genome methylation and miRNA expression microarrays will be used to search candidate genes for teenager smoking exposure. We plan to develop a prediction model for immunotoxicological reaction by utilizing epigenetic signature data from microRNA expression and DNA methylation profiles based on machine learning methodologies. We will also establish a personalized epigenetic prediction model for allergy development and build the risk assessment platform for immunotoxicological reaction under tobacco smoke exposure. Finally, we will examine the causal relationship between epigenetic signatures and immunotoxicological reactions under an independent children's cohort.